The tyrosine kinase activity of the ABL1 protein is normally tightly regulated, with the N-terminal cap region of the SH3 domain playing an important role. One regulatory mechanism involves the N-terminal cap glycine-2 residue being myristoylated and then interacting with a myristate binding site within the SH1 catalytic domain. A hallmark of chronic myeloid leukemia (CML) is the Philadelphia chromosome (Ph), formed by the t(9,22) reciprocal chromosome translocation in a haematopoietic stem cell. This chromosome carries the BCR-ABL1 oncogene which encodes the chimeric BCR-ABL1 protein, that lacks the N-terminal cap and has a constitutively active tyrosine kinase domain.
Although drugs that inhibit the tyrosine kinase activity of BCR-ABL1 via an ATP-competitive mechanism, such as Gleevec®/Glivec® (imatinib), Tasigna® (nilotinib) and Sprycel® (dasatinib), are effective in the treatment of CML, some patients relapse due to the emergence of drug-resistant clones, in which mutations in the SH1 domain compromise inhibitor binding. Although Tasigna® and Sprycel® maintain efficacy towards many Gleevec-resistant mutant forms of BCR-ABL1, the mutation in which the threonine-315 residue is replaced by an isoleucine (T315I) remains insensitive to all three drugs and can result in CML patients developing resistance to therapy. Therefore, inhibiting BCR-ABL1 mutations, such as T315I, remains an unmet medical need. In addition to CML, BCR-ABL1 fusion proteins are causative in a percentage of acute lymphocytic leukemias, and drugs targeting ABL kinase activity also have utility in this indication.
Agents targeting the myristoyl binding site (so-called allosteric inhibitors) have potential for the treatment of BCR-ABL1 disorders (J. Zhang, F. J. Adrian, W. Jahnke, S. W. Cowan-Jacob, A. G. Li, R. E. Iacob4, T. Sim, J. Powers, C. Dierks, F. Sun, G.-R. Guo, Q. Ding, B. Okram, Y. Choi, A. Wojciechowski, X. Deng, G. Liu, G. Fendrich, A. Strauss, N. Vajpai, S. Grzesiek, T. Tuntland, Y. Liu, B. Bursulaya, M. Azam, P. W. Manley, J. R. Engen, G. Q. Daley, M. Warmuth, N. S. Gray. Targeting Bcr-Abl by combining allosteric with ATP-binding-site inhibitors. Nature 2010; 463:501-6). To prevent the emergence of drug resistance from ATP inhibitor and/or allosteric inhibitor use, a combination treatment using both types of inhibitor can be developed for the treatment of BCR-ABL1 related disorders. In particular, the need exists for small molecules, or combinations thereof, that inhibit the activity of BCR-ABL1 and BCR-ABL1 mutations via the ATP binding site, the myristoyl binding site or a combination of both sites.
Further, compounds of the invention as inhibitors of ABL1 kinase activity have the potential to be used as therapies for the treatment of metastatic invasive carcinomas and viral infections such as pox and Ebola viruses.
The compounds from the present invention also have the potential to treat or prevent diseases or disorders associated with abnormally activated kinase activity of wild-type Abl, including non-malignant diseases or disorders, such as CNS diseases in particular neurodegenerative diseases (for example Alzheimer's, Parkinson's diseases), motoneuroneuron diseases (amyotophic lateral sclerosis), muscular dystrophies, autoimmune and inflammatory diseases (diabetes and pulmonary fibrosis), viral infections, prion diseases.